That’s the flavor of the taco. Otherwise it’s just meat in flatbread.
You are telling on yourself by saying “some people don’t like it hot”. There are many peppers that are not hot: ancho chiles, chile del arbol, Anaheim pepper, poblanos, banana peppers, cascabel, chilaca, etc.
If you don’t know about mild peppers, you don’t know about Mexican food. It’s just that simple. Downvote away Europeans.